Rule 1 

"Do not act incautiously when confronting little bald wrinkly smiling men."

A line from Terry Pratchet's novel, the Thief of Time, spoken by Lu Tze the sweeper.

"Always remember rule 1."

Rule 1 by Tim the Creator October 31, 2012

Rule Of 10

According to the Rule of 10, No one is allowed to call someone after 10pm or before 10am unless it is absolutely Important.

*ring ring*
Bob: uhhg, hello?
John: hey. what's up?
Bob: Why the hell did you call me, it's... 2am...
John: Oh, I just got out of the club, I was seeing what you were doing.
Bob: Did you forget the Rule Of 10?

Rule Of 10 by Immortal-Jake August 14, 2007

Rule 34 

If you've thought of it, it's already porn.

Or will be.

Person 1: I wonder if there is Pokemon Porn?
Person 2: Rule 34
Person 1: What?
Person 2: Yes, there is.

Rule 34 by Redracoon August 3, 2010

Rule 3 

Rule of the internet
"We are anonymous"

12 yr old kid: who are you guys?
other person: hey kid, rule 3

Rule 3 by demolishun November 6, 2012

Rule Number One 

Don't post useless definitions on UD. Namely you, chris.

omfg i gotz teh bestest ideea evar! i iz gona postt thaat im coolz undur teh definition "Rule Number One"! geenius!

Rule Number One by Karonaway December 3, 2007

Rule 99 

Every video of Russia is always dreary on top, white on bottom and something smacks into something else. Occasionally if you're lucky you'll see something explode.

OP never said this was from Russia, because of Rule 99 we all just knew.

Rule 99 by SubbyG February 17, 2013

Rule #4 

Rule #4 is a rule that states you must respect women at all time, and you must never pressure them with unwanted romantic advances. It is used to keep lacrosse players everywhere off the shit list

Chad: "grabs chicks ass at a party"
Brad: bro what are you doing!? Rule #4 bro!
Chad: holy shit bro I'm so sorry your right, rule #4
Chad: I'm sorry that I disrespected your personal space Jill, please forgive me

Rule #4 by SadFart64 October 1, 2019